Increased bulk density powders and polymers containing them

ABSTRACT

The invention provides a treated powder having improved loose bulk density comprising a silanized inorganic powder treated with a long chain fatty acid or salts thereof, wherein the amount of the long chain fatty acid is about 0.25% to about 2 wt %, based on the total weight of the treated powder.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of Ser. No. 11/486,287 filed on Jul.13, 2006 which claims the benefit of U.S. Provisional Application No.60/700,065, filed Jul. 18, 2005, which are incorporated by reference intheir entireties.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to treated inorganic powders, moreparticularly treated titanium dioxide, having an improved loose bulkdensity; a process for their preparation; and their use in polymercompositions.

2. Description of the Related Art

High molecular weight polymers, for example, hydrocarbon polymers andpolyamides, are melt extruded into shaped structures such as tubing,pipe, wire coating or film by well-known procedures wherein a rotatingscrew pushes a viscous polymer melt through an extruder barrel into adie in which the polymer is shaped to the desired form, and is thensubsequently cooled and solidified into a product, that is, theextrudate, having the general shape of the die. In film blowingprocesses, as an extruded plastic tube emerges from the die the tube iscontinuously inflated by air, cooled, collapsed by rolls and wound up onsubsequent rolls.

Inorganic powders can be added to the polymers for various reasons. Inparticular, titanium dioxide pigments, are added to polymers forimparting whiteness and/or opacity to the finished article. To deliverother properties to the molded part or film, additional additives areusually incorporated into the processing step.

In a typical method for combining inorganic powders and polymers thepowder and polymer are dropped through a feed tube into the feed barrelnear the starting end of an extruder or into a “side stuffer” part-wayalong the extruder's length. The combined powders and polymers arecompounded and extruded.

In another typical method for combining inorganic powders and polymers,the inorganic powder can be dropped with the polymer into the cavity ofa rotational blender such as a Banbury.

For ease of processing, it is desirable for bulk dry powders used asingredients in industrial operations, and in polymer compositions inparticular, to flow freely. One measure of the free-flow property of apowder is bulk flow. Bulk flow is a general term that describes theflowability of a powder in storage and handling systems. One measure ofbulk flow is the Rat Hole Index (RHI) as measured by a Johanson Hang-upIndicizer which is described herein below.

In the field of compounding inorganic powders with polymers, the powdersare typically received by the polymer compounder in packages containingfrom 20 kg to more than 20 tons. Smaller package volumes (typically upto 1 metric ton) are added to the process via small hoppers or “daybins” that can store sufficient powder for production periods rangingbetween a few minutes and a full day. Larger packages (from 1 to 20-25tons) are typically unloaded into silos that may contain sufficientpowder for many days of production. This unloading and powder transfermay be performed by pneumatic or mechanical conveyors or simple gravitychutes. In all of these cases, it is desirable for the powder to havesufficient flowability to discharge reliably from the hopper or silowithout blockages and, preferably, without the need for extraordinaryflow promotion efforts. Many inorganic powders, especially titaniumdioxide, are known for having poor flow properties, as compared tofree-flowing materials such as dry sand or plastic pellets. Handlingsystems for the subject materials are frequently operating near theirlimits; consequently, powder treatments that reduce the flowability ofthe dry bulk powder increase the compounder's handling costs. Inparticular, arching (bridging) and a related form of flow obstructionknown as ratholing may occur with powders that have poor flowproperties, making it difficult if not impossible to empty the silo orhopper without extensive human intervention which may require processshutdown. Powder flow properties also affect the filling of the screwflights of metering screws and feed screws of extruders. Poor flowingpowders tend to not fill the flights in a consistent way, and also notfill them as completely as a more flowable powder would. This reducesboth the uniformity (accuracy) of a screw transport system and also itsdelivery capacity.

The need for improved productivity through higher output of compoundedpolymer is a constant issue with both blending and compounding methods.In each method, the production rate can be limited by the physicalvolume of the apparatus used to introduce the mixture of inorganicpowder and polymer into the process. Since the feeding devices arelimited by volume, not mass, increasing the loose bulk density of theinorganic powder (the density of the powder in loose form) is onepossible way to increase the mass that can be processed. Both methodsrequire that the powder flow readily into the reaction chamber. In thecase of the extruder, the rate at which the compounding can occur may belimited by the transport capacity (volume per revolution) of therotating screw. If the powder has a higher loose bulk density, more masscan be transported per revolution of the screw, resulting in higheroutput. Similarly the total output of a rotational blender may belimited by the volume occupied by the individual components prior toblending. To improve the productivity of these blenders, it is desirableto decrease the amount of space a given mass powder component takes up.Therefore, if the loose bulk density of the inorganic powder isincreased, it will take up less volume and increase the overall outputof the blender.

While higher values of loose bulk density, in themselves, are beneficialfor bulk flow, some titanium dioxide pigments with high loose bulkdensity are also highly compressible. The compressibility is indicativeof interparticle packing which results in greater cohesive strength andpoor bulk flow.

In addition, powder treating techniques, in particular treatment withorganosilicon compounds to improve performance properties such as lacingresistance in a polyolefin matrix, can have a detrimental impact on thebulk flow properties of the powder.

A treatment for inorganic powders which improves the loose bulk densityof the powder without a significant impact on bulk flow has beendiscovered.

SUMMARY OF THE DISCLOSURE

The disclosure relates to a treated powder having improved loose bulkdensity comprising a silanized inorganic powder treated with a longchain fatty acid or salts thereof, wherein the amount of the long chainfatty acid is about 0.25% to about 2 wt %, based on the total weight ofthe treated powder, and wherein the loose bulk density of the treatedpowder is greater than the loose bulk density of an untreated silanizedinorganic powder, processes for making the treated powder, polymercompositions comprising the treated powder and processes for making thepolymer.

The disclosure can provide a treated powder having improved loose bulkdensity with minimal disruption in bulk flow comprising a silanizedinorganic powder treated with a long chain fatty acid and salts thereof;wherein the long chain fatty acid or salt thereof is present in anamount of about 0.25 weight % to about 2 wt %, based on the total weightof the treated powder.

In one embodiment, the loose bulk density, of the treated powder is atleast about 1.0% greater than the loose bulk density of an untreatedsilanized inorganic powder, typically about 3 or above, more typicallyabout 4 to about 50%, greater than the loose bulk density of anuntreated silanized inorganic powder, and still more typically about 10to about 45% greater than the loose bulk density of an untreatedsilanized inorganic powder by weight, based on the entire weight of thepowder.

The powder may be a pigment or a nanoparticle.

The disclosure provides treated powder wherein the long chain fatty acidmay have up to about 30 carbon atoms, typically from about 8 to about 30carbon atoms, more typically from about 10 to about 20 carbon atoms.They can be selected from the group of lauric acid, stearic acid,isostearic, oleic acid, linoleic acid, and mixture of one or morethereof.

The disclosure provides an inorganic powder that may be selected fromZnS, TiO₂, CaCO₃, BaSO₄, ZnO, MoS₂, silica, talc and clay, and moretypically TiO₂.

The disclosure provides a treated powder wherein the silanized inorganicpowder comprises at least one silane, or a mixture of at least onesilane and at least one polysiloxane. The silane may have the formula:

R¹ _(x)Si(R²)_(4-x)

-   -   wherein:    -   R¹ is a nonhydrolyzable aliphatic, cycloaliphatic or aromatic        group having at least 1 to about 20 carbon atoms;    -   R² is a hydrolyzable group such as an alkoxy, halogen, acetoxy        or hydroxy group or mixture thereof; and    -   x is an integer ranging from 1 up to and including 3.

The disclosure provides a treated powder wherein the silane may beselected from the group of octyltriethoxysilane, nonyltriethoxysilane,decyltriethoxysilane, dodecyltriethoxysilane, tridecyltriethoxysilane,tetradecyltriethoxysilane, pentadecyltriethoxysilane,hexadecyltriethoxysilane, heptadecyltriethoxysilane,aminotriethoxysilane, aminotrimethoxysilane, vinyltriethoxysilane orvinyltrimethoxysilane and octadecyltriethoxysilane. In the treatedpowder, the silane may comprise R¹ which is a straight chain or branchedhydrocarbon containing 8 up to and including 18 carbon atoms; R² ischloro, methoxy, ethoxy or hydroxy group or mixtures thereof; and x isan integer ranging from 1 up to and including 3. Alternately, in thetreated powder, the silane may comprise R¹ a straight chain or branchedhydrocarbon containing 8 up to and including 18 carbon atoms; R² is anethoxy group; and x is an integer ranging from 1 up to and including 3.

Alternately, the disclosure provides a treated powder wherein thepolysiloxanes may have the formula:

(R³ _(n)SiO_((4-n)/2))_(m)

-   -   wherein:    -   R³ is an organic or inorganic group;    -   n ranges from 0 up to and including 3; and    -   m is an integer greater than or equal to 2.        The siloxane may be selected from the group polydimethylsiloxane        (PDMS), vinyl phenylmethyl terminated dimethyl siloxanes, and        divinylmethyl terminated polydimethyl siloxane. The ratio of        silane to polysiloxane may be 1:2 to 2:1, and more typically        1:1.

The disclosure provides a process of preparing a treated powder havingimproved loose bulk density comprising mixing a silanized inorganicpowder with a long chain fatty acid and salts thereof, typically a Na orK salt thereof; wherein long chain fatty acid or salt thereof is presentin the amount of about 0.25 weight % to about 2 wt %, based on the totalweight of the treated powder.

The loose bulk density of the treated powder of this disclosure, can beat least about 1%, typically at least about 3.0% greater than the loosebulk density of an untreated silanized inorganic powder, more typicallyat least about 4 to about 50% greater than the loose bulk density of anuntreated silanized inorganic powder, and still more typically about 10to about 45% greater than the loose bulk density an untreated silanizedinorganic powder by weight, based on the entire weight of the powder.

In one embodiment, the loose bulk density of the treated titaniumdioxide, can be at least about 1% up to and including about 40%, moretypically at least about 6% to about 40% greater than the loose bulkdensity of untreated silanized titanium dioxide by weight, based on theentire weight of the titanium dioxide.

The disclosure provides a process wherein the mixing is accomplishedusing a V-cone blender fitted with an internal disperser at ambienttemperature for about 15 minutes.

The disclosure provides a process wherein the mixing is accomplished byspraying the long chain fatty acid or salt thereof and at least onesilane, or a mixture of at least one silane and at least onepolysiloxane on the inorganic powder while the powder is mechanicallyagitated.

Alternately, the mixing may be accomplished by:

(i) metering at least one silane, or a mixture of at least one silaneand at least one polysiloxane, and the long chain fatty acid or saltthereof into a flow restrictor, having an inlet and an outlet, with airor some other motive gas, to create a zone of turbulence at the outletof the flow restrictor thereby atomizing the at least one silane, or amixture of at least one silane and at least one polysiloxane, and thelong chain fatty acid or salt thereof to form an atomized liquid; and

(ii) contacting the inorganic powder with the atomized liquid to form atreated powder comprising the inorganic powder, at least one silane, ora mixture of at least one silane and at least one polysiloxane, and thelong chain fatty acid or salt thereof. The atomized liquid may besubstantially uniformly coated on the surface of the inorganic powder.

DETAILED DESCRIPTION OF THE DISCLOSURE

The disclosure relates to a process for treating an inorganic powder,typically a titanium dioxide powder, to form a powder capable of beingdispersed into a polymer melt for preparing a plastic part. The treatedpowder may be present in the amount of about 0.25 weight % to about 2.0wt %, more typically in the amount of about 0.5 weight % to about 1.0 wt%, based on the total weight of the treated powder. The loose bulkdensity of the treated powder can be at least about 1%, typically atleast about 3.0%, greater than the loose bulk density of an untreatedsilanized inorganic powder, more typically about 4 to about 50 greaterthan the loose bulk density of an untreated silanized inorganic powder,and still more typically about 10 to about 45% greater than the loosebulk density of an untreated silanized inorganic powder, by weight basedon the entire weight of the powder.

Treated Powder:

It is contemplated that any inorganic powder will benefit from thesurface treatment of this disclosure. By inorganic powder it is meant aninorganic particulate material that becomes uniformly dispersedthroughout a polymer melt that can impart color and opacity to thepolymer melt. Some examples of inorganic powders include but are notlimited to ZnS, TiO₂, CaCO₃, BaSO₄, ZnO, MoS₂, silica, talc and clay.

In particular, titanium dioxide is an especially useful powder in theprocesses and products of this disclosure. Titanium dioxide (TiO₂)powder useful in the present disclosure may be in the rutile or anatasecrystalline form. It is commonly made by either a chloride process or asulfate process. In the chloride process, TiCl₄ is oxidized to TiO₂powders. In the sulfate process, sulfuric acid and ore containingtitanium are dissolved, and the resulting solution goes through a seriesof steps to yield TiO₂. Both the sulfate and chloride processes aredescribed in greater detail in “The Pigment Handbook”, Vol. 1, 2nd Ed.,John Wiley & Sons, NY (1988), the teachings of which are incorporatedherein by reference. The powder may be a pigment or nanoparticle.

By “pigment” it is meant that the titanium dioxide powders have anaverage size of less than about 1 micron. Typically, the powders have anaverage size of from about 0.020 to about 0.95 microns, more typically,about 0.050 to about 0.75 microns and most typically about 0.075 toabout 0.50 microns. Pigmentary titanium dioxide more typically rangesfrom about 0.15 to about 0.8 microns, and more typically from about 0.2to about 0.4 microns in average size diameter.

By “nanoparticle” it is meant that the primary titanium dioxide powderstypically have an average particle size diameter of less than about 100nanometers (nm) as determined by dynamic light scattering that measuresthe particle size distribution of particles in liquid suspension. Theparticles are typically agglomerates that may range from about 3 nm toabout 6000 nm. More specifically, the primary particles typically existin air as agglomerates ranging from about 3000 nm to about 6000 nm.

The titanium dioxide powder may be substantially pure titanium dioxideor may contain other metal oxides, such as silica, alumina, zirconia.Other metal oxides may become incorporated into the powders, forexample, by co-oxidizing or co-precipitating titanium compounds withother metal compounds. If co-oxidized or co-precipitated up to about 20wt % of the metal oxide, more typically, 0.5 to 17 wt %, most typicallyabout 0.7 to about 17 wt % may be present, based on the total powderweight.

The titanium dioxide powder may also bear one or more metal oxidesurface treatments. These treatments may be applied using techniquesknown by those skilled in the art. Examples of metal oxide treatmentsinclude silica, alumina, and/or zirconia among others. Such treatmentsmay be present in an amount of about 0.1 to about 10 wt %, based on thetotal weight of the powder, preferably about 0.5 to about 3 wt %.

The inorganic powder may be silanized by treating with at least onesilane, or a mixture of at least one silane and at least onepolysiloxane. The silane comprises a silane monomer. Suitable silanemonomers are those in which at least one substituent group of the silanecontains an organic substituent. The organic substituent can containheteroatoms such oxygen or halogen. Typical examples of suitable silanesinclude, without limit, alkoxy silanes and halosilanes having thegeneral formula:

R¹ _(x)Si(R²)_(4-x)

-   -   wherein:    -   R¹ is a nonhydrolyzable aliphatic, cycloaliphatic or aromatic        group having at least 1 to about 20 carbon atoms;    -   R² is a hydrolyzable group such as an alkoxy, halogen, acetoxy        or hydroxy group or mixtures thereof; and    -   x is an integer ranging from 1 up to and including 3.        Typically R¹ is a nonhydrolyzable aliphatic group of the        structure:

wherein R^(a) is a C₁-C₂₀ hydrocarbon, and X=Cl, Br, or HSO₄ and Me ismethyl.

The nonhydrolyzable group will not react with water to form a differentgroup. The hydrolysable group will react with water to form one or moredifferent groups, which become adsorbed or chemically bonded to thesurface of the titanium dioxide powder. Typically, R¹ is an alkoxy grouphaving about 1 to about 4 carbon atoms, preferably, ethoxy or methoxy; ahalogen, such as chloro or bromo; or acetoxy or hydroxy or mixturethereof. Preferably R¹ is chloro, methoxy, ethoxy, hydroxy, or mixturethereof. Typically, R² is a straight chain or branched chain alkyl groupsuch as, but not limited to, octyl, decyl, hexadecyl, or octadecyl.

Some useful silanes may be selected from the group of 3-trimethoxysilylpropyl octyl dimethyl ammonium chloride, 3-trimethoxysilyl propyl octyldimethyl ammonium chloride, 3-trimethoxysilyl propyl decyl dimethylammonium chloride, 3-trimethoxysilyl propyl hexadecyl dimethyl ammoniumchloride, and 3-trimethoxysilyl propyl octadecyl dimethyl ammoniumchloride.

A siloxane may be used in combination with the silane to surface treatthe inorganic powder. Typically, the siloxane may have a reactive site,and a silicon-hydrogen bond may form the reactive site of the siloxanepolymer. The siloxane may be a polysiloxane which may have the formula:

(R³ _(n)SiO_((4-n)/2))_(m)

-   -   wherein    -   R³ is an organic or inorganic group;    -   n is an integer ranging from 0 up to and including 3; and    -   m is an integer greater than or equal to 2.

Hydridosiloxanes are typical examples of useful siloxanes having asilicon-hydrogen reactive site. Such hydridosiloxanes includealkylhydridosiloxanes in which the alkyl group contains from 1 to about20 carbon atoms. Specifically methylhydridosiloxanes can be useful suchas those having the formula Me₃SiO[SiOMeH]_(n)—[SiOMe₂]_(m)—SiMe₃, wheren and m are independently integers from 1 to about 200 and Me is methyl.Other potentially useful siloxane compounds having a reactive site arethe hydridosilsesquioxanes described in U.S. Pat. No. 6,572,974.

The siloxane may be selected from the group polydimethylsiloxane (PDMS),vinyl phenylmethyl terminated dimethyl siloxanes, and divinylmethylterminated polydimethyl siloxane and the like.

The silane or combination of silane and siloxane may be present in theamount of about 0.1 to about 5 weight %, based on the total amount ofthe treated powder. The ratio of silane to polysiloxane may be 1:2 to2:1, and more typically 1:1.

The inorganic powder may be treated, additionally surface treated, byadding to the powder one or more of the long chain fatty acids or saltsthereof of this disclosure that may have greater than about 8 carbonatoms, typically from about 8 to about 30 carbon atoms, more typicallyfrom about 10 to about 20 carbon atoms.

Typically the fatty acid of this disclosure is a saturated orunsaturated, straight chain or branched chain fatty acid. Yet moretypically the fatty acid is a liquid at room temperature or slightlyelevated temperature, more typically at temperatures ranging from about20° C. up to about 40° C.

In one embodiment, the fatty acid can be methyl branched, for example,without limitation thereto, isostearic acid.

In another embodiment, the fatty acid can be monounsaturated orpolyunsaturated. An example of a useful monounsaturated fatty acid,without limitation thereto, is oleic acid. If the fatty acid ispolyunsaturated it can contain less than five conjugated or unconjugateddouble bonds. An example of a useful polyunsaturated fatty acid islinoleic acid.

The fatty acids may be selected from the group of lauric acid, stearicacid, isostearic, oleic acid, linoleic acid, and mixture thereof.

The fatty acid can be an alkali or alkaline earth metal salt. Examplesof useful alkali or alkaline earth metals are sodium, potassium andmagnesium.

The long chain fatty acid may be present in the amount of about 0.25weight % to about 2 wt %, and more typically about 0.5 weight % to about1.0 wt %, based on the total weight of the treated powder.

By “surface treated” it is meant inorganic powders, in particulartitanium dioxide powders, that have been contacted with the compoundsdescribed herein. Typically, the compounds are adsorbed on the surfaceof the powder or a reaction product of at least one of the compoundswith the powder is present on the surface as an adsorbed species orchemically bonded to the surface. The compounds or their reactionproducts or combination thereof may be present as a coating, continuousor discontinuous, on the surface of the powder. Typically, a continuouscoating comprising the fatty acid and the silane, siloxane or mixturesthereof, is on the surface of the powder.

The silanized inorganic powders may be prepared by a process thatcomprises surface treating powders with the silane or combination ofsilane and siloxane. This process is not especially critical and may beaccomplished in a number of ways. While typically the powder may betreated with the silane, if present, and then the siloxane compound insequence, the powder may be treated with the silane and the siloxanecompound simultaneously.

The surface treatment of the powder may be performed by contacting drypowder with neat compound or in an appropriate solvent that one skilledin the art can select. When a silane is employed the compound may beprehydrolzyed, then contacted with dry powder.

Alternatively, the treating compounds may be dissolved in a solvent orprepared as a slurry before contacting powder, in dry or slurry form. Inaddition, the powder may be immersed in the treating compound, ifliquid, or a solution, of the treating compound or compounds is used.

Any of a variety of mixing processes and mixing devices therefor whichare well known in the art of powder treating can be used. High shearmixing is especially useful. For example, mixing may be accomplished inany high shear mixing apparatus including but not limited to a V-coneblender fitted with an internal stirring bar at ambient temperature fora period of time, for example, while not being limited there to, about15 minutes.

Powders can be treated while being agitated by a shaker or otherpulsating device, while falling from one container to another, whiletumbling in a moving vessel or a vessel with rotating paddles that canmechanically fluidize the mixture such as a Forberg mixer. Additionally,the powders can be treated by vigorous shaking or lifting and dividingthe powder and spraying the mixture while it is contained in a closedvolume substantially larger than the volume of the powder. This can beaccomplished on a small scale by shaking the ingredients while they arecontained in a closed bag for a period of time. The treatment time canrange from 10-15 minutes. A substantially shorter time is needed with aForberg mixer. A double cone blender with intensifier bars andLittleford-type mixers can also be used.

Mixing may also be accomplished by:

(i) metering treating agents comprising a long chain fatty acid or saltthereof, a silane and optionally a siloxane into a flow restrictor,having an inlet and an outlet, with air or some other motive gas, tocreate a zone of turbulence at the outlet of the flow restrictor therebyatomizing the treating agents to form an atomized liquid; and

(ii) contacting the inorganic powder with the atomized liquid, typicallyby dispersing the inorganic powder and simultaneously or subsequentlycontacting the inorganic powder with the atomized liquid, to form atreated powder comprising or derived from inorganic powder and thetreating agents. The atomized liquid may be substantially uniformlycoated on the surface of the inorganic powder. The foregoing mixingprocess involves dispersion of the liquid and the powder in a region ofhigh shear.

Polymers:

The melt-processable polymer that can be employed together with thetreated powder of this disclosure comprises a high molecular weightpolymer.

Polymers useful in this disclosure are high molecular weight meltprocessable polymers. By “high molecular weight” it is meant to describepolymers having a melt index value of 0.01 to 50, typically from 2 to 10as measured by ASTM method D1238-98. By “melt-processable,” it is meanta polymer that can be extruded or otherwise converted into shapedarticles through a stage that involves obtaining the polymer in a moltenstate.

Polymers which are suitable for use in this disclosure include, by wayof example but not limited thereto, polymers of ethylenicallyunsaturated monomers including olefins such as polyethylene,polypropylene, polybutylene, and copolymers of ethylene with higherolefins such as alpha olefins containing 4 to 10 carbon atoms or vinylacetate; vinyls such as polyvinyl chloride, polyvinyl esters such aspolyvinyl acetate, polystyrene, acrylic homopolymers and copolymers;phenolics; alkyds; amino resins; epoxy resins, polyamides,polyurethanes; phenoxy resins, polysulfones; polycarbonates; polyestersand chlorinated polyesters; polyethers; acetal resins; polyimides; andpolyoxyethylenes. Mixtures of polymers are also contemplated.

Polymers suitable for use in the present disclosure also include variousrubbers and/or elastomers, either natural or synthetic polymers based oncopolymerization, grafting, or physical blending of various dienemonomers with the above-mentioned polymers, all as generally known inthe art.

Typically, the polymer may be selected from the group consisting ofpolyolefin, polyvinyl chloride, polyamide and polyester, and mixture ofthese. More typically used polymers are polyolefins. Most typically usedpolymers are polyolefins selected from the group consisting ofpolyethylene, polypropylene, and mixture thereof. A typical polyethylenepolymer is low density polyethylene and linear low density polyethylene.

Other Additives

A wide variety of additives may be present in the polymer compositionproduced by the process of this disclosure as necessary, desirable orconventional. Such additives include polymer processing aids such asfluoropolymers, fluoroelastomers, etc., catalysts, initiators,anti-oxidants (e.g., hindered phenol such as butylated hydroxytoluene),blowing agent, ultraviolet light stabilizers (e.g., hindered amine lightstabilizers or “HALS”), organic pigments including tinctorial pigments,plasticizers, antiblocking agents (e.g. clay, talc, calcium carbonate,silica, silicone oil, and the like) leveling agents, flame retardants,anti-cratering additives, and the like.

Preparation of the Polymer Composition

The present disclosure provides a process for preparing apowder-containing, high molecular weight polymer composition.

In one embodiment of the disclosure, the treated powder may be contactedwith a first high molecular weight melt processable polymer. Any meltcompounding techniques, known to those skilled in the art may be used.Generally, the treated powder, other additives and melt-processablepolymer are brought together and combined in a blending operation, suchas dry blending, that applies shear to the polymer melt to form thepowder containing, more typically pigmented, polymer. Themelt-processable polymer is usually available in the form of powder,granules, pellets or cubes. Methods for dry blending include shaking ina bag or tumbling in a closed container. Other methods include blendingusing agitators or paddles. Treated powder, and melt-processable polymermay be co-fed using screw devices, which mix the treated powder, polymerand melt-processable polymer together before the polymer reaches amolten state. Alternately, the components may be fed separately intoequipment where they may be melt blended, using any methods known in theart, including screw feeders, kneaders, high shear mixers, blendingmixers, and the like. Typical methods use Banbury mixers, single andtwin screw extruders, and hybrid continuous mixers.

Processing temperatures depend on the polymer and the blending methodused, and are well known to those skilled in the art. The intensity ofmixing depends on the polymer characteristics.

The treated powder containing polymer composition produced by theprocess of this disclosure is useful in production of shaped articles.The amount of powder present in the powdered polymer composition andshaped polymer article will vary depending on the end use application.

In one embodiment of this invention a first melt processable polymercontaining the inorganic oxide forms what is referred to as a“masterbatch” which is prepared by melt blending the polymer andinorganic oxide. Any polymer which is suitable for melt processing witha high concentration of inorganic oxide is suitable for the polymer ofthe masterbatch.

The masterbatch is then melt blended with a second melt processablepolymer referred to as a “let down” polymer. Any polymer suitable forthe desired end-use can be used as the let down polymer.

The first and second polymers can be the same or different. Typically,the first and second polymers are highly compatible. The second polymeris usually free of inorganic oxide but can contain one or more otheradditives (such as an antiblock agent or antioxidant) which can be addedby melt blending from a masterbatch containing the polymer and suchother additive.

While the amount of first polymer can vary depending on the polymer ormixture of polymers employed, the first polymer is typically present inan amount of from about 10 to about 60 wt. %, typically about 20 toabout 50 wt %, even more typically about 30 to about 40 wt. %. based onthe total weight of the first and second polymers.

The amount of inorganic oxide in the polymer composition can range fromabout 30 to about 90 wt %, based on the total weight of the composition,preferably, about 50 to about 80 wt %. The amount of inorganic oxide inan end use, such as a shaped article, for example, a polymer film, canrange from about 0.01 to about 20 wt %, and is preferably from about 0.1to about 15 wt %, more preferably 5 to 10 wt %, based on the entireweight of the article.

A shaped article is typically produced by melt blending the treatedinorganic oxide containing polymer which comprises a first highmolecular weight melt-processable polymer, with a second high molecularweight melt-processable polymer to produce the polymer that can be usedto form the finished article of manufacture. The treated inorganic oxidecontaining polymer composition and second high molecular weight polymerare melt blended, using any means known in the art, as disclosedhereinabove. In this process, twin-screw extruders are commonly used.Co-rotating twin-screw extruders are available from Werner andPfleiderer. The melt blended polymer is extruded to form a shapedarticle.

The treated inorganic oxide of this invention may be employed in any ofa wide variety of melt processable polymer compositions and processesutilizing them which are well known in the industry for making plasticarticles. For example, the polymer composition together with theinorganic oxide can be used in the extrusion of sheets, films and shapedproducts; pultrusion; coextrusion; ram extrusion; spinning; blown film;injection molding; insert molding; isostatic molding; compressionmolding; rotomolding; thermoforming; sputter coating; lamination; wirecoating; calendaring; welding; powder coating. Particularly suitableshaped articles are tubing, pipes, wire coatings, sheet and films,especially blown films.

EXAMPLES Loose Bulk Density (BD) Measurement

Loose bulk density (BD) was measured as the most loosely packed bulkdensity when a material was left to settle by gravity alone. The loosebulk density utilized in these examples was measured using a GilsonCompany nominal 3 inch sieve pan having a volume of 150.6 cm³. Thematerial was hand sieved through a 10 mesh sieve over the tared sievepan until overfilled. The top was scraped level using a large spatulablade at a 45° angle from the horizontal, taking care not to tamp orcompress the contents of the cup. The cup was then weighed and the loosebulk density was then calculated.

Rathole Index (RHI) Measurement:

The measured parameter referred to as rathole index (RHI), describes thedegree of difficulty that can be expected in handling a powder.Typically the bulk flow of rutile titanium dioxide has a RHI of about 10to about 24.

Powder flowability, particularly in silo and hopper situations, can bedescribed using a variety of shear cell testing devices. One such deviceis the Johanson Hang-up Indicizer from Johanson Innovations. TheIndicizer device compresses a sample of powder to a pre-determinedcompaction stress and then measures the force necessary to press a punchthrough the compacted powder. From the measured force, and a concurrentmeasurement of the volume of the powder following compaction, theIndicizer calculates an estimate of the propensity of the powder to forma rathole-type flow obstruction. The predetermined compaction stresslevel corresponds to an estimate of the stress in a silo. In theseexamples, the prototypical silo is considered to be 10 feet in diameter,and the Indicizer sets the compaction stress accordingly. The calculatedparameter is known as rathole index (RHI) and describes the degree ofdifficulty that can be expected in handling a powder. Larger values ofthe RHI correspond to greater amounts of difficulty expected in handlingthe powder.

To obtain the test results reported in the Examples, a sample of eachpowder was carefully spooned into the test cell after being sievedthrough a 16-mesh sieve. Filling continued until the chamber wasapproximately 75% full. The cell was carefully weighed and thenpositioned into the Indicizer testing device. The powder weight and itsvolume were considered by the automated tester in both the calculationof the silo stresses and also the calculated propensity of the materialto form a rathole. After the user input the sample weight and nominalsilo diameter, the automated tester completed the test and displayed itsestimated value of RHI.

Example 1

Rutile titanium dioxide pigment (DuPont Ti-Pure® R104) was surfacetreated with cis-9-octadecanoic acid (oleic acid, 99+%, Aldrich) atvarious levels using the method as described in U.S. Pat. No. 4,303,702.The treated pigment was measured for loose bulk density. Resultsreported in Table 1 show a significant increase in the loose bulkdensity of the treated sample versus a comparative example similarlyprepared but without the oleic acid.

TABLE 1 Loose bulk density of oleic acid treated titanium dioxide LooseBD % Change Sample (g/cc) vs. Control R104 + 0% oleic acid 0.584 —R104 + 0.25 wt. % oleic acid 0.639 +9.4 R104 + 0.5 wt. % oleic acid0.646 +10.6 R104 + 0.83 wt. % oleic acid 0.620 +6.2

Example 2

500 g samples of rutile titanium dioxide pigment (DuPont Ti-Pure® R104)were surface treated with cis-9-octadecanoic acid (oleic acid, 99+%,Aldrich) at various levels by diluting the desired amount of oleic acidwith hexanes to a total volume of 20 mL. The oleic acid solution wasplaced into a clean and dry squirt bottle. The pigment was placed in aclean and dry, aluminum foil lined pan and spread uniformly to a depthof ≦1.5 cm. The pigment was uniformly sprayed with the oleic acidsolution present in the squirt bottle. Once the surface of the pigmenthad been wetted, the pigment was uniformly turned over using a spoon.Uniformly spraying the squirt bottle solution onto the overturnedpigment was continued, and the steps of uniformly turning over thepigment and spraying were repeated until the squirt bottle was empty.The treated pigment was added to a clean and dry plastic bag and thecontents of the bag were thoroughly shaken for a minimum of 3 minutes.The mixed, treated pigment was placed into a clean and dry, aluminumfoil lined pan (the pigment was lightly covered with aluminum foil) andplaced into a laboratory hood overnight to air dry. The air-driedpigment was then placed into a 120° C. oven and dried for exactly onehour. The loose bulk density was measured per the standard methoddocumented above. The results of this treatment are reported in Table 2and show an increase in loose bulk density versus a comparative samplesimilarly prepared but without oleic acid.

TABLE 2 Loose bulk density of oleic acid treated titanium dioxide LooseBD % Change Sample (g/cc) vs. Control R104 + 0% oleic acid .93 — R104 +0.5 wt. % oleic acid 1.00 +7.5 R104 + 1.0 wt. % oleic acid 1.22 +31.2R104 + 2 wt. % oleic acid 1.16 +24.7 R104 + 3 wt. % oleic acid 1.3 +39.8

Example 3

500 g sample of zinc oxide (Zano®, Umicore Netherland) was surfacetreated with 1 wt % octyltriethoxysilane (Aldrich) andcis-9-octadecanoic acid (oleic acid, 99+%, Aldrich) at 0.5 wt % levelusing the method described in Example 2. The loose bulk density of thissample was measured versus a comparative sample similarly prepared butwithout the octadecanoic acid and the results are reported in Table 3.The data show an increase in loose bulk density versus the comparativeexample.

TABLE 3 Loose Bulk Density of Zinc Oxide Treated with Oleic Acid LooseBD % Change Sample (g/cc) vs. Control ZnO + 0 wt. % oleic acid 0.30 —ZnO + 1 wt. % oleic acid 0.31 3.3%

Example 4

500 g samples of rutile titanium dioxide (Ti-Pure® R104) were surfacetreated with various fatty acids using the method described in Example2. The loose bulk densities of these samples were measured versus acomparative sample similarly prepared but without the fatty acidadditive and the results are reported in Table 4. The data showincreases in loose bulk density versus the comparative sample for allthe samples with the cis-9,12-octadecadienoic (linolenic acid, Aldrich,99%) being the most effective.

TABLE 4 Loose Bulk Density of Titanium Dioxide Treated with Fatty AcidLoose BD % Change Sample (g/cc) vs. Control R104 + 0% fatty acid 0.95 —R104 + 0.5 wt. % linolenic acid 0.99 +4.2 R104 + 1.0 wt. % linolenicacid 1.09 +14.7 R104 + 0.5 wt. % isostearic acid 0.96 +1.1 R104 + 1.0wt. % isostearic acid 0.99 +4.2

Example 5

1000 g samples of rutile titanium dioxides (Ti-Pure® R104 and R101) weresurface treated with cis-9-octadecanoic acid (oleic acid, 99+%, Aldrich)at 0.5 and 1.0 wt % level using the method described in Example 2. Theloose bulk density and RHI of these samples were compared to comparativesamples similarly prepared but without the octadecanoic acid, and theresults are reported in Table 5. The data show an increase in loose bulkdensity versus the comparative sample. The data also show that thesamples that have a silane treatment in addition to the oleic acid(compare R104 vs R101) show minimal disruption in bulk flow. While theRHI value is higher for with the addition of oleic acid it is stillwithin an acceptable range for ease of handling.

TABLE 5 Loose Bulk Density of Titanium Dioxide Treated with Oleic AcidLoose BD % Change Sample (g/cc) vs. Control RHI R101 + 0% fatty acid0.60 — 14.5 R101 + 0.5 wt % Oleic Acid 0.66 +10.0 15.4 R101 + 1.0 wt %Oleic Acid 0.72 +20.0 17.2 R104 + 0% fatty acid 0.96 — 21.3 R104 + 0.5wt % Oleic Acid 1.01  +5.2 20.9 R104 + 1.0 wt % Oleic Acid 1.06 +11.0 22

1. A treated powder having improved loose bulk density comprising asilanized inorganic powder treated with a long chain fatty acid or saltsthereof, wherein the amount of the long chain fatty acid is about 0.25%to about 2 wt %, based on the total weight of the treated powder, andwherein the loose bulk density of the treated powder is greater than theloose bulk density of an untreated silanized inorganic powder.
 2. Thetreated powder of claim 1 wherein the long chain fatty acid has a chainlength of about 8 to about 30 carbon atoms.
 3. The treated powder ofclaim 2 wherein the long chain fatty acid has a chain length of about 10to about 20 carbon atoms.
 4. The treated powder of claim 1 wherein thesilanized inorganic powder comprises at least one silane, or a mixtureof at least one silane and at least one polysiloxane.
 5. The treatedpowder of claim 4 wherein the silane has the formula:R¹ _(x)Si(R²)4-x wherein: R¹ is a nonhydrolyzable aliphatic,cycloaliphatic or aromatic group having at least 1 to about 20 carbonatoms; R² is a hydrolyzable group selected from the group consisting ofalkoxy, halogen, acetoxy or hydroxy or mixtures thereof; and x is aninteger of 1 up to and including
 3. 6. The treated powder of claim 4wherein the silane is selected from the group of octyltriethoxysilane,nonyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane,tridecyltriethoxysilane, tetradecyltriethoxysilane,pentadecyltriethoxysilane, hexadecyltriethoxysilane,heptadecyltriethoxysilane and octadecyltriethoxysilane.
 7. The treatedpowder of claim 5 wherein in the silane, R¹ is a hydrocarbon having 8 to18 carbon atoms; R² is an ethoxy group; and x is an integer ranging from1 up to and including
 3. 8. The treated powder of claim 4 wherein thepolysiloxane has the formula:(R³ _(n)SiO_((4-n))/2)m wherein R³ is an organic or inorganic group; nis ranges from 0 up to and including 3; and m is an integer greater thanor equal to
 2. 9. The treated powder of claim 8 wherein the siloxane isselected from polydimethylsiloxane, vinyl phenylmethyl terminateddimethyl siloxanes, and divinylmethyl terminated polydimethyl siloxane.10. The treated powder of claim 8 wherein the siloxane ispolydimethylsiloxane.
 11. The treated powder of claim 1 wherein theinorganic powder is selected from ZnS, TiO₂, CaCO₃, BaSO₄, ZnO, MoS₂,talc and clay.
 12. The treated powder of claim 11 wherein the inorganicpowder is TiO₂.
 13. The treated powder of claim 12 wherein the loosebulk density of the treated TiO₂ is at least about 1% to about 40%greater than the loose bulk density of an untreated silanized TiO₂ byweight, based on the entire weight of the titanium dioxide. 14-27.(canceled)